Thanks for all your replies. I'm very interested in any chances you make to improve the performance. On my site you can download the latest version with a improved shader. With this shader I get FPS between 12 and 20.
Good New you can now download the first rough version of LandGen from my site
I hope the installation works. I haven't tested it.
Here some of possibilities for seed improvement that work but reduce the quality.
1. the tip TheComet; reduce the camera range. Don't forget to make the skydome smaller otherwise the sky will disappear and reduce the radius of the sun and moon.
2. In cover.dba reduce the constant gField. This constant defines the amount of ground cover. gField = 50 gives you an array of 50 by 50 objects around the player. If you reduce gField maybe you have to increase gSpread. This defines the distance between the objects.
3. in ReadData.dba after the line
AllObjects(Array Count(AllObjects())).maxLoaded = DataFile Integer(1)
add the line
AllObjects(Array Count(AllObjects())).maxLoaded = 10
And after the line
AllObjects(Array Count(AllObjects())).maxBBLoaded = DataFile Integer(1)
add the line
AllObjects(Array Count(AllObjects())).maxBBLoaded = 100
The first defines how many objects of one type (tree) are loaded at same time (now 50). The second does the same for the billboard lod's (now 1000).